Different Amplifier Qualities? Same actual RMS power but different sound?

[sundownz Pro Seller]

Only if there is an [audible] difference in distortion/noise or frequency response (and a difference in frequency response is easily "fixed" with an EQ). And most any amplifier produced today will have low (inaudible) amounts of THD+N, especially in a subbass application where distortion is harder to identify.

While I am with you that any modern unit pretty much sounds passable at normal levels, but when you push many of these units hard to the point of their rated power output the THD can easily reach unpleasant levels.

This has proven to be the case with the inexpensive HiFonics units that reach levels of 10% THD to achieve rated output power. Combine this with the THD of a subwoofer at that amount of power input and you have a level that is easily detectable even with subbass.

If you still do not agree that this is true compare something like a Lanzar Vibe 1200D to an expensive Class-D such as Xtant X1001 even at a moderate level. I think alot of the problem is that many manufacturers skimp on the MOSFETs used in this design, not taking into account the special needs of a Class-D design and/or not caring for cost reasons.

As to the earlier mention to RCs test, it has no relevance here. His test is to show that different topologies will sound the same if their response is equalized and THD is even -- that is a no brainer. In a fully built retail amplifier unit these factors are NOT equal between different models. Amp A may have 10% THD at 1000 watts whereas Amp B has 0.1% THD at 1000 watts, you have 1000 watts in both cases, which one do you want?

 

[JimJ 5,000+ posts]

This thread makes me giggle.

Right [there].

 

[Ctesibius 10+ year member]

While I am with you that any modern unit pretty much sounds passable at normal levels, but when you push many of these units hard to the point of their rated power output the THD can easily reach unpleasant levels.

Most amplifiers should be capable of 1-2% THD at their rated output level, given that the amplifier is not overrated. This is the distortion level most amplifiers are rated at, and IIRC the distortion level set forth in the [voluntary] CEA-2006 rating standard.

This has proven to be the case with the inexpensive HiFonics units that reach levels of 10% THD to achieve rated output power. Combine this with the THD of a subwoofer at that amount of power input and you have a level that is easily detectable even with subbass.

And that amplifier was overrated. At a power level of around 1kw it was still under 1% THD+N.

What does this tell us? Not to push the amplifier beyond ~1kw of output. Obviously such levels of distortion would be audible. Which means any prudent installer would not set the amplifier up in such a manor to allow such distortion levels.

Yes, this means that you can not push the amplifier to it's rated power. But it is still possible to use the amplifier in a manor such that the distortion is managable. The useable power output of an amplifier is limited to it's "clean" power output, not to what's printed on the box.

If you still do not agree that this is true compare something like a Lanzar Vibe 1200D to an expensive Class-D such as Xtant X1001 even at a moderate level.

The Vibe 1200D tested by Car Sound was capable of 1200w @ .8% THD+N on 14.4V. So I'm not really sure what you're trying to say here.

As to the earlier mention to RCs test, it has no relevance here.

The test is totally relevant here. If you do not understand why, then you do not understand the challenge.

Refer back to the original post, and apply what RC's amplifier challenge has (thus far) proven. The implications should quickly become obvious.

His test is to show that different topologies will sound the same if their response is equalized and THD is even -- that is a no brainer.

It also shows at what point frequency response and THD cause audible changes in sound.

I would venture to say right now, given that statement, that you don't actually fully comprehend RC's amplifier challenge and what it proves/disproves.

It establishes tolerances for audibility of certain aspects of an amplifier, among other things.

In a fully built retail amplifier unit these factors are NOT equal between different models. Amp A may have 10% THD at 1000 watts whereas Amp B has 0.1% THD at 1000 watts, you have 1000 watts in both cases, which one do you want?

Guess what that means? Don't power amp A to 1kw of output, as it obviously is not within the amplifiers linear limits. Amp A is not truly a 1kw amplifier. That is all your example shows.

 

[Ctesibius 10+ year member]

This thread makes me giggle.
Right [there].

Thank you for that not-so-thoughtful insight.

It was a huge contribution to the thread.

 

[JimJ 5,000+ posts]

Thank you for that not-so-thoughtful insight.
It was a huge contribution to the thread.

You're welcome //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[snb778 5,000+ posts]

all those links were great and all....but they just opened up soo many more points to argue there....people are interpreting a lot of what was said in those links differently...therefor leading to other confusions and arguments.

i saw people saying a watt is a watt, then others saying, NO, what it was saying was.....a watt is a watt, but in different conditions it doesnt sound the same, or some said "a watt isnt a watt" ...and around we go.

 

[Ctesibius 10+ year member]

all those links were great and all....but they just opened up soo many more points to argue there....people are interpreting a lot of what was said in those links differently...therefor leading to other confusions and arguments.
i saw people saying a watt is a watt, then others saying, NO, what it was saying was.....a watt is a watt, but in different conditions it doesnt sound the same, or some said "a watt isnt a watt" ...and around we go.

I can see how someone could read those links and come up with "points to argue"....but those people only simply read the links, but didn't actually comprehend what was being said.

If you actually comprehend what was being discussed, and not just read through it, there really is nothing to argue.

 

[sundownz Pro Seller]

Most amplifiers should be capable of 1-2% THD at their rated output level, given that the amplifier is not overrated. This is the distortion level most amplifiers are rated at, and IIRC the distortion level set forth in the [voluntary] CEA-2006 rating standard.
And that amplifier was overrated. At a power level of around 1kw it was still under 1% THD+N.

What does this tell us? Not to push the amplifier beyond ~1kw of output. Obviously such levels of distortion would be audible. Which means any prudent installer would not set the amplifier up in such a manor to allow such distortion levels.

Yes, this means that you can not push the amplifier to it's rated power. But it is still possible to use the amplifier in a manor such that the distortion is managable. The useable power output of an amplifier is limited to it's "clean" power output, not to what's printed on the box.

The Vibe 1200D tested by Car Sound was capable of 1200w @ .8% THD+N on 14.4V. So I'm not really sure what you're trying to say here.

The test is totally relevant here. If you do not understand why, then you do not understand the challenge.

Refer back to the original post, and apply what RC's amplifier challenge has (thus far) proven. The implications should quickly become obvious.

It also shows at what point frequency response and THD cause audible changes in sound.

I would venture to say right now, given that statement, that you don't actually fully comprehend RC's amplifier challenge and what it proves/disproves.

It establishes tolerances for audibility of certain aspects of an amplifier, among other things.

Guess what that means? Don't power amp A to 1kw of output, as it obviously is not within the amplifiers linear limits. Amp A is not truly a 1kw amplifier. That is all your example shows.

I suppose I was a bit fuzzy on RCs test, for some reason I incorrectly thought that he bypassed everything except the output stage. This does not appear to be the case upon re-reading it. So as far as his test goes, in his environment, I agree with it.

His test aims to prove that with a scientifically sound test setup you cannot tell the difference between two amplifiers, which it appears to prove very well. But this environment is tightly controlled, whereas your car is not.

RC seems to indicate that regulation can cause audible differences in the amp test post, "as for regulation it is a FACT that a amp that has a unregulated supply vs a regulated supply (by regulation i am referring to the secondary voltage rails not the input regulation) will produce more unclipped power reproducing MUSIC than another amp that HAS THE EXACT SAME CONTINUOUS POWER RATING."

Now maybe that is what causes the difference I was thinking of in a real environment, varying levels of regulation causing very much so audible level differences. Match the levels by reducing the output away from the limits and you remove the difference, so in RCs conditions this difference would never be heard although in your listening it very well may be. In the above case two amps equally rated with a standard power measurement, which is done on a pure wave, COULD sound different when a music signal is applied. Is this not a correct conclusion?

-

I would also like to restate my last paragraph in my earlier post, instead of targeting RC's test what I intended to direct the .1% vs 10% THD @ 1000 watts statement towards was the statement "a watt is a watt." For some reason I wasn't thinking correctly earlier and was associated the common misconception of what the test says with what it really says, I hadn't read it since 2002 prior to this post.

 

[thch 10+ year member]

quick notes -- you have to assume certain things about amps. some interesting notes:

well, one issue is that the amp's ratings are done with a resistive load. its fairly easy to build an amp to work well with a resistive load. using a reactive load can change things quite a bit.

in my experience, i've gotten an amp to oscillate at about 1000hz. the amp would play a certain note and then afterwards it would add a 1000hz tone into the output. this tone wasn't in the original recording -- it was added by the amp.

 

[sundownz Pro Seller]

Also... the test is not entirely scientific to start with upon further consideration. It has too many variables. You don't just vary the amp, you also have a human element. Sensory memory only lasts a few seconds, and by some estimates only a few hundred milliseconds.

Lets say someone did hear a difference, that doesn't mean they can remember the difference and pick it out 12 times in a row. What I'm saying is you may know that something is different but if required to identify it time and time again you will fail since your sensory memory is so short you forget what you heard.

Even if it makes it to short term memory that is generally limited to 7 items... now think about how much information you are taking in from the music all at once. It would be difficult to move information to long term memory about such fine details as people perceive between amplifiers since they are so small and numerous that they would pretty much flood out the short term memory.

Now... the overall sound is something that is easily recognized. The tune, the lyrics, etc are easy to recall. But fine details like dynamic distortions, slight differences in frequency response, etc probably don't make it past the sensory memory.

"In adults, auditory afterimages can be studied by presenting two very brief sounds in succession. If the sounds' onsets are closer together than about 1/4 second, the second sound tends to interrupt the identification of the first by interfering with the use of the first sound's afterimage."

-- http://www.missouri.edu/~psycowan/research.html --

So am I saying that I can pass RCs test? Nope. I'm just saying that it would be impossible for anyone to do it even if an audible difference was present.

If someone knows something I do not about acoustic memory I would be more than happy to read it. I just thought about it this morning and did some quick searching online to reach the above conclusion.

 

[amartin_72]

So my question , will an ED Nine.1 rated at 1200w@12.5 volts and 13-1400 Actual RMS wattage off 14.4 volts be a noticable upgrade / worth the money from my Kenwood which is 1016 watts at 14.v volts and of "lesser build quality".

 

[msimon 10+ year member]

Also... the test is not entirely scientific to start with upon further consideration. It has too many variables. You don't just vary the amp, you also have a human element. Sensory memory only lasts a few seconds, and by some estimates only a few hundred milliseconds.
Lets say someone did hear a difference, that doesn't mean they can remember the difference and pick it out 12 times in a row. What I'm saying is you may know that something is different but if required to identify it time and time again you will fail since your sensory memory is so short you forget what you heard.

Even if it makes it to short term memory that is generally limited to 7 items... now think about how much information you are taking in from the music all at once. It would be difficult to move information to long term memory about such fine details as people perceive between amplifiers since they are so small and numerous that they would pretty much flood out the short term memory.

Now... the overall sound is something that is easily recognized. The tune, the lyrics, etc are easy to recall. But fine details like dynamic distortions, slight differences in frequency response, etc probably don't make it past the sensory memory.

"In adults, auditory afterimages can be studied by presenting two very brief sounds in succession. If the sounds' onsets are closer together than about 1/4 second, the second sound tends to interrupt the identification of the first by interfering with the use of the first sound's afterimage."

-- http://www.missouri.edu/~psycowan/research.html --

So am I saying that I can pass RCs test? Nope. I'm just saying that it would be impossible for anyone to do it even if an audible difference was present.

If someone knows something I do not about acoustic memory I would be more than happy to read it. I just thought about it this morning and did some quick searching online to reach the above conclusion.

If this was true wouldn't all sq competition be pointless? How can a judge compare a car he is listening to, to a reference system that he heard days/hours ago?

 

[spudracer326 10+ year member]

I can see how someone could read those links and come up with "points to argue"....but those people only simply read the links, but didn't actually comprehend what was being said.
If you actually comprehend what was being discussed, and not just read through it, there really is nothing to argue.

dude...grow up or gtfo

 

[tRiGgEr 5,000+ posts]

dude...grow up or gtfo

//content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

 

[sundownz Pro Seller]

If this was true wouldn't all sq competition be pointless? How can a judge compare a car he is listening to, to a reference system that he heard days/hours ago?

What I'm about to say is just my take on the situation... I could be wrong. I don't have any references for it, and if someone can jump in and confirm or disprove any of it that is welcome.

I would assume that BIG differences would be much easier to recall. For instance, I can recall that the only MB Quart tweeters I have ever heard really hurt my ears. Speakers have such a big difference between them that it should be retainable, the main points about them at least (eg: bright, dull, boomy, etc). For instance I can recall that the system in my old car had great bass up front and a high sound stage... these aren't really complex things about the system, but are critical parts of an SQ system.

I also doubt that even the most golden earned judge out there can recall ALL the subtle details of a system he heard long ago or even an hour ago. For that matter, SQ competitions are so subjective it's pretty much pointless as it is, maybe the judge liked it today but he wouldn't tomorrow. That is an ongoing debate in competition circuits... SPL is you and the meter, SQ adds the human element that can easily be wrong.